01 - Preheat oven to 375°F and grease a 9x13-inch baking dish.
02 - Boil pasta in salted water until al dente according to package directions. Drain thoroughly.
03 - Sauté diced onion in a skillet over medium heat for 3 minutes until softened. Add minced garlic and cook 1 minute longer.
04 - Add cooked chicken, crumbled bacon, thawed peas, salt, pepper, smoked paprika, and thyme to the skillet. Remove from heat.
05 - Whisk together sour cream, softened cream cheese, whole milk, and 2 cups shredded cheddar in a large bowl until smooth.
06 - Add drained pasta and chicken mixture to the cheese sauce. Stir until evenly coated throughout.
07 - Spread the mixture evenly into the prepared baking dish.
08 - Combine panko breadcrumbs, melted butter, and remaining ½ cup cheddar cheese in a small bowl.
09 - Sprinkle the breadcrumb mixture evenly over the top of the casserole.
10 - Bake for 25-30 minutes until the top is golden brown and the casserole is bubbling around the edges.
11 - Let the casserole rest for 5 minutes before serving to allow it to set.